As well known, in a power plant a steam dump device is typically located downstream a bypass line arranged between the boiler and the condenser. Such bypass line is required, for example, during start-up or run-down operations of the plant where the steam has a high content of water which could damage the turbine blading.
The turbine bypass system hence permits start-up and rapid turbine load reductions, which includes turbine tripping, without causing a reactor trip or relief valve operation. The function of the dump steam diffusers is to breakdown the pressure of the dump steam in stages and to de-superheat it before it enters in the condenser.
To this purpose, the steam dump device permits the introduction of the steam into the condenser by operating a reduction of its temperature and the pressure values.
Generally, the steam dump device includes a vessel comprising means to reduce pressure and temperature of the steam and to efficiently guide the steam into the condenser.
U.S. Pat. No. 6,189,871, with reference to FIG. 1, discloses a partial external installation of a steam dump device 1 arranged on a bypass line connecting the boiler to the condenser 9. In particular, the steam dump device 1 includes a first perforated diaphragm 3, a cooling chamber 4 and a second perforated diaphragm 8.
The second perforated diaphragm 8 of the cooling chamber 4 projects into the condenser neck 7 of the condenser 9.
Patent publication JP61285386, with reference to FIG. 2, teaches a partially external installation steam dump device constituted in a double structure form including spray nozzles provided on the wall surface of the device.
Lastly, patent publication JP57049004 discloses a steam dump device, depicted in FIG. 3, having a configuration aiming to prevent a internal protection of a barrel body of a condenser caused by in-flow of bypassing steam, wherein a cooling means is arranged in a turbine bypass inlet pipe as a double pipe structure near an open end of the condenser of a turbine bypass pipe.
However, solutions above illustrated still don't provide an optimum efficiency in terms of properly guiding the steam into the condenser avoiding damages of the condenser neck due to vibration and/or thermal expansion and large flow of nuclear power plants.